Download 10 Fingers By Aka
Jacalyn Loston
A finger is a prominent digit on the forelimbs of most tetrapod vertebrate animals, especially those with prehensile extremities (i.e. hands) such as humans and other primates. Most tetrapods have five digits (pentadactyly),[1][2] and short digits (i.e. significantly shorter than the metacarpal/metatarsals) are typically referred to as toes, while those that are notably elongated are called fingers. In humans, the fingers are flexibly articulated and opposable, serving as an important organ of tactile sensation and fine movements, which are crucial to the dexterity of the hands and the ability to grasp and manipulate objects.
As terrestrial vertebrates were evolved from lobe-finned fish, their forelimbs are phylogenetically equivalent to the pectoral fins of fish. Within the taxa of the terrestrial vertebrates, the basic pentadactyl plan, and thus also the metacarpals and phalanges, undergo many variations.[3]Morphologically the different fingers of terrestrial vertebrates are homolog. The wings of birds and those of bats are not homologous, they are analogue flight organs. However, the phalanges within them are homologous.[4]
Chimpanzees have lower limbs that are specialized for manipulation, and (arguably) have fingers (instead of toes) on their lower limbs as well. In the case of primates in general, the digits of the hand are overwhelmingly referred to as "fingers".[5][6] Primate fingers have both fingernails and fingerprints.[7]
Research has been carried out on the embryonic development of domestic chickens showing that an interdigital webbing forms between the tissues that become the toes, which subsequently regresses by apoptosis. If apoptosis fails to occur, the interdigital skin remains intact. Many animals have developed webbed feet or skin between the fingers from this like the Wallace's flying frog.[8][9][10]
The palm has five bones known as metacarpal bones, one to each of the five digits. Human hands contain fourteen digital bones, also called phalanges, or phalanx bones: two in the thumb (the thumb has no middle phalanx) and three in each of the four fingers. These are the distal phalanx, carrying the nail, the middle phalanx, and the proximal phalanx.Joints are formed wherever two or more of these bones meet. Each of the fingers has three joints:
Each finger may flex and extend, abduct and adduct, and so also circumduct. Flexion is by far the strongest movement. In humans, there are two large muscles that produce flexion of each finger, and additional muscles that augment the movement. The muscle bulks that move each finger may be partly blended, and the tendons may be attached to each other by a net of fibrous tissue, preventing completely free movement. Although each finger seems to move independently, moving one finger also moves the other fingers slightly which is called finger interdependence or finger enslaving.[14][15][16]
Muscles of the fingers can be subdivided into extrinsic and intrinsic muscles.The extrinsic muscles are the long flexors and extensors. They are called extrinsic because the muscle belly is located on the forearm.
The fingers have two long flexors, located on the underside of the forearm. They insert by tendons to the phalanges of the fingers. The deep flexor attaches to the distal phalanx, and the superficial flexor attaches to the middle phalanx. The flexors allow for the actual bending of the fingers. The thumb has one long flexor and a short flexor in the thenar muscle group. The human thumb also has other muscles in the thenar group (opponens and abductor brevis muscle), moving the thumb in opposition, making grasping possible.
The extensors are located on the back of the forearm and are connected in a more complex way than the flexors to the dorsum of the fingers. The tendons unite with the interosseous and lumbrical muscles to form the extensorhood mechanism. The primary function of the extensors is to straighten out the digits. The thumb has two extensors in the forearm; the tendons of these form the anatomical snuff box. Also, the index finger and the little finger have an extra extensor, used for instance for pointing. The extensors are situated within six separate compartments. The first compartment contains abductor pollicis longus and extensor pollicis brevis. The second compartment contains extensors carpi radialis longus and brevis. The third compartment contains extensor pollicis longus. The extensor digitorum indicis and extensor digitorum communis are within the fourth compartment. Extensor digiti minimi is in the fifth, and extensor carpi ulnaris is in the sixth.
Aside from the genitals, the fingertips possess the highest concentration of touch receptors and thermoreceptors among all areas of the human skin,[citation needed] making them extremely sensitive to temperature, pressure, vibration, texture and moisture. Recent studies[when?] suggest fingers can feel nano-scale wrinkles on a seemingly smooth surface, a level of sensitivity not previously recorded.[17] This makes the fingers commonly used sensory probes to ascertain properties of objects encountered in the world, making them prone to injury.
Although a common phenomenon, the underlying functions and mechanism of fingertip wrinkling following immersion in water are relatively unexplored. Originally it was assumed[by whom?] that the wrinkles were simply the result of the skin swelling in water,[citation needed] but it is now understood that the furrows are caused by the blood vessels constricting due to signalling by the sympathetic nervous system in response to water exposure.[19][20] One hypothesis for why this occurs, the "rain tread" hypothesis, posits that the wrinkles may help the fingers grip things when wet, possibly being an adaption from a time when humans dealt with rain and dew in forested primate habitats.[19] A 2013 study supporting this hypothesis found that the wrinkled fingertips provided better handling of wet objects but gave no advantage for handling dry objects.[21] However, a 2014 study attempting to reproduce these results was unable to demonstrate any improvement of handling wet objects with wrinkled fingertips.[20]
The somatosensory cortex representation of the hand is a dynamic reflection of the fingers on the external hand: in syndactyly people have a clubhand of webbed, shortened fingers. However, not only are the fingers of their hands fused, but the cortical maps of their individual fingers also form a club hand. The fingers can be surgically divided to make a more useful hand. Surgeons did this at the Institute of Reconstructive Plastic Surgery in New York to a 32-year-old man with the initials O. G.. They touched O. G.'s fingers before and after surgery while using MRI brain scans. Before the surgery, the fingers mapped onto his brain were fused close together; afterward, the maps of his individual fingers did indeed separate and take the layout corresponding to a normal hand.[27]
A rare anatomical variation affects 1 in 500 humans, in which the individual has more than the usual number of digits; this is known as polydactyly. A human may also be born without one or more fingers or underdevelopment of some fingers such as symbrachydactyly. Extra fingers can be functional. One individual with seven fingers not only used them but claimed that they "gave him some advantages in playing the piano".[28]
The fingers are commonly affected by diseases such as rheumatoid arthritis and gout. Diabetics often use the fingers to obtain blood samples for regular blood sugar testing. Raynaud's phenomenon and Paroxysmal hand hematoma are neurovascular disorders that affect the fingers.
Research has linked the ratio of lengths between the index and ring fingers to higher levels of testosterone, and to various physical and behavioral traits such as penis length[29] and risk for development of alcohol dependence[30] or video game addiction.[31]
The name pinkie derives from Dutch pinkje, of uncertain origin. In English only the digits on the hand are known as fingers. However, in some languages the translated version of fingers can mean either the digits on the hand or feet. In English a digit on a foot has the distinct name of toe.
Trigger finger makes a finger get stuck in a bent position. It may straighten suddenly with a snap. The fingers most often affected are the ring finger and the thumb, but the condition can affect any finger.
Your child will start to use fingers to pick up food. This helps your baby develop fine motor skills. Offer your baby finger foods that are small enough to pick up and soft enough to chew. Here are some examples:
Clubbing may result from chronic low blood-oxygen levels. This can be seen with cystic fibrosis, congenital cyanotic heart disease, and several other diseases. The tips of the fingers enlarge and the nails become extremely curved from front to back.
Clubbed fingers is a symptom of disease, often of the heart or lungs which cause chronically low blood levels of oxygen. Diseases which cause malabsorption, such as cystic fibrosis or celiac disease can also cause clubbing.
Approximately 40,000 Americans have lost part of their arms above the wrist. However, there are around 500,000 who have lost one or more fingers, 110,000 of whom are women by best estimates. While there are many prostheses available for people without hands, far fewer exist for people with finger loss.
The finger replacement, now sold as the Point Digit by a company called Point Design, LLC, is made from 3D-printed titanium with semi-hollow construction, allowing the fingers to be strong while not being heavy. The prosthetic digits can be bent and locked into one of 11 different positions through a unique ratcheting mechanism and linkage bars developed by the researchers. They return to a fully extended position at the touch of a button or by fully flexing the digit, which engages an auto spring-back feature.
The full fingers currently come in six different sizes. At a 2020 conference hosted by the Institute of Biomedical Engineering, the research team submitted a paper unveiling a smaller version of the Point Digit suitable for smaller women and for children as young as five years old. The team hopes to conduct a study in the near future on the usefulness of the smaller hand by giving it to users to take home and test.
f448fe82f3